1. Field of the Invention
This invention relates to an improvement in a scanning system for use with reproducing machines and in one aspect to an improvement in the drive for scanning carriages affording minimal shock to the machine during total scanning cycle.
2. Description of the Prior Art
This invention refers to an improvement in scanning exposure systems. It is common in optical copying of documents that the subject is placed on a stationary optical exposure support and the optical exposure device includes a lens by which an image is transferred to the copy material along a ray path. This is commonly done by moving an exposure light source and a series of mirrors on a carriage past the orginal. Then, successive incremental regions from the document to be copied are imaged onto the image-receiving member by the mirrors and a lens. This scanning technique has been utilized to reduce the size of the machine and to permit the use of a less expensive objective lens than a machine which exposes the entire original onto the receptor simultaneously.
Prior known systems for scanning the original document by the use of a pair of relatively movable carriages supporting mirrors for transferring the successive images include U.S. Pat. No. 3,330,181, issued July 11, 1967 to H. Jakobson; U.S. Pat. No. 3,431,053, issued Mar. 4, 1969 to R. Wick et al; U.S. Pat. No. 3,832,057, issued Aug. 27, 1974 to D. K. Shogren; and U.S. Pat. No. 3,858,976, issued Jan. 7, 1975 to E. R. Brooke.
The devices disclosed in these patents have similar arrangements comprising a first carriage for the illuminating device, a mirror and the exposure aperture and a second carriage movable relative to the first and carrying a mirror or mirrors for directing an image to an objective lens. The two carriages are relatively movable so that, on movement of one, the other moves half the distance travelled by the first but in the same direction. This ensures that the optical path from the original to the lens is always the same length regardless of the position of the part with the slot shaped exposure aperture. These prior devices utilize complex drive systems such as catch release mechanisms, contoured cable wind-up pulleys, dash pots, and other systems to move the carriages relative to the lens. Typical also, when the carriages have moved past the document support surface to project the image therefrom to the image receiving surface of the copying apparatus, the carriage is automatically returned to the starting position so that the apparatus is ready to make the next copy. These return movements of the carriages are generally made by the force of a spring which rapidly drives the carriage back to the start position. These mechanisms and systems have provided inadequate control resulting in high random acceleration levels, undesirable vibrations, and noise. These systems generally require more components and have not had the reliability required. Therefore, these problems have been reviewed and the present invention is believed to solve the shock, vibration, noise and reliability problems.
The present invention simplifies the drive system for a scanning exposure device. The present invention utilizes a drive system which by its nature removes shock due to uncontrolled acceleration or deceleration of the movable elements.
The drive system of the present invention utilizes a cam and linkage drive to the principal carriage such that the acceleration, velocity and displacement of the movable carriages are continuously controlled. The only other presently known cam drive for a scanning exposure device is U.S. Pat. No. 3,612,679, issued Oct. 12, 1971 to F. D. Punnett et al. In this patent the exposure device comprises an aperture and illuminating device movable across the optical exposure support and a lens is movably supported intermediate the scanning apparatus and the image-receiving member and movable relative thereto to project the sequential images onto the image-receiving member.
In the scanning system of this patent it is necessary to have a straight optical path necessitating an enlarged machine and it is necessary that the lens support, during its movement, be free of any vibrations to have good resolution of the projected image on the image receptor of the copying apparatus. Further, this patent teaches the desirability of the rapid return of the scanning members to the start position upon completion of the scanning mode which is accomplished through spring 75 and the relationship of the follower 74 on the cam 73.
Therefore, the prior art sets forth numerous ways of functionally providing for the scan exposure of a photo-conductive surface or other image receptor but the solution to the problems encountered by these devices have previously continued unattended.